Dark Lightning Zaps Airline Passengers

A jet plane flies past a mushroom-like cloud in Beijing, China, on June 14, 2012. The cloud took about one hour and ten minutes to form, and was followed by lightning inside it, and maybe dark lightning as well.

Corbis

Gallery

Earth'sBlueMarbleBeauty:Photos

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Western Hemisphere
Feb. 24, 2012 -- We at Discovery News are loving the new photos of Earth coming in from VIIRS, the biggest and most important instrument of the five aboard NASA's Earth-observing satellite - Suomi NPP. These composite images are put together using a number of swaths of the Earth's surface taken with the Visible/Infrared Imager Radiometer Suite (VIIRS) over the course of a day as the Suomi NPP satellite orbits the planet from pole to pole. Here we see the western hemisphere from swaths taken on Jan. 4, 2012.

NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

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Eastern Hemisphere
The Suomi NPP satellite flew over the eastern hemisphere six times during an eight hour time period on Jan 23, 2012. NASA scientist Norman Kuring took those six sets of data and combined them into this image shown here.

NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

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Australian View
Here NASA scientist Norman Kuring has done the same with the VIIRS data sets taken on Feb. 8, 2012.

NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

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Arctic View
The newly launched Suomi National Polar-orbiting Partnership (S-NPP) satellite, which was blasted into space on Oct. 28, 2011, circled the Earth 15 times to capture the visual data used for the stunning picture.
BIG PIC: White Marble View Over Arctic

NASA/GSFC/Suomi NPP.

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Hot and Cold
Here we see the results of the Clouds and the Earth's Radiant Energy System (CERES) instrument at work on the Suomi NPP satellite.
"In the longwave image, heat energy radiated from Earth (in watts per square meter) is shown in shades of yellow, red, blue and white. The brightest-yellow areas are the hottest and are emitting the most energy out to space, while the dark blue areas and the bright white clouds are much colder, emitting the least energy. Increasing temperature, decreasing water vapor, and decreasing clouds will all tend to increase the ability of Earth to shed heat out to space," the NASA CERES team explained.

NASA/NOAA/CERES Team

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Keeping Up with the Sun
From its vantage 824 kilometers (512 miles) above Earth, the Visible Infrared Imager Radiometer Suite (VIIRS) on the NPOESS Preparatory Project (NPP) satellite gets a complete view of our planet every day. This image from Nov. 24, 2011, was the first complete global image from VIIRS.
Rising from the south and setting in the north on the daylight side of Earth, VIIRS images the surface in long wedges measuring 3,000 kilometers (1,900 miles) across. The swaths from each successive orbit overlap one another, so that at the end of the day, the sensor has a complete view of the globe. The Arctic is missing because it is too dark to view in visible light during the winter.
The NPP satellite was placed in a Sun-synchronous orbit, a unique path that takes the satellite over the equator at the same local (ground) time in every orbit. So, when NPP flies over Kenya, it is about 1:30 p.m. on the ground. When NPP reaches Gabon—about 3,000 kilometers to the west—on the next orbit, it is close to 1:30 p.m. on the ground. This orbit allows the satellite to maintain the same angle between the Earth and the Sun so that all images have similar lighting.
The consistent lighting is evident in the daily global image. Stripes of sunlight (sunglint) reflect off the ocean in the same place on the left side of every swath. The consistent angle is important because it allows scientists to compare images from year to year without worrying about extreme changes in shadows and lighting.
PHOTOS: Sunsets and Other Sky Wonders

Image by NASA’s NPP Land Product Evaluation

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Final Checks
Electro Magnetic Interference testing of the Suomi NPP satellite at the Ball Aerospace facility.

NASA/Ball Aerospace

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Behind the Scenes
By stitching six swaths together, NASA scientist Norman Kuring takes the Suomi NPP satellite perspective from its polar orbit around Earth at an altitude of 512 miles (about 824 kilometers), and changes it to a 'Blue Marble' view as though it were seen from 7,918 miles (about 12,743 kilometers).
NEWS: Earth's Mugshot Explained

You’ve probably never seen it, but it’s possible you’ve been exposed to it if you’ve ever flown through a thunderstorm. Dark lightning, flashes of gamma rays that occur at altitudes in which commercial aircraft fly, doesn’t produce much light, but it does produce radiation.

New research presented Wednesday at a meeting of the European Geosciences Union in Vienna pinpoints the amount of radiation that dark lightning produces -- and how much pilots and passengers might be getting exposed to.

“The good news is that the doses are not super scary -- it could be worse,” said lead research Joseph Dwyer, a physics professor at Florida Institute of Technology. “It’s similar to going to the doctor’s office and getting a CT scan.”

The existence of dark lightning itself was discovered on a NASA spacecraft in 1994. In the electrical fields of a thunderstorm, electrons zoom close to the speed of light, colliding with atoms to emit the gamma rays.

In 2010, Dwyer and colleagues determined that dark lightning occurred at altitudes where airplanes commonly fly. That prompted the current work, which involved a physics-based model that can show exactly how the discharge happens.

The preliminary work showed how much radiation was being emitted, but the size of the space it was produced in was unclear. With the current model, Dwyer’s team was able to pinpoint the exposure dose that someone on an airplane would likely receive.

“This work is very important because it gets you into the zone where you start to understand how often and how likely they are to happen,” said University of California Santa Cruz physics professor David Smith, who has worked with Dwyer but was not involved in the modeling work.

The next step, Smith said, is to start determining how often the flashes occur. Because the bursts are so brief -- about 10-100 of microseconds -- they are usually undetected, although it’s possible you could see a diffuse, purple light, Dwyer said.

“Unless you have gamma ray detectors on board, no one would think anything of it,” Smith said.

The National Science Foundation is currently working on an armored plane that could fly through thunderstorms, Smith said. If an instrument were placed on board, researchers may begin to get a better idea of the frequency of the flashes. Currently, the bursts are thought to occur much less frequently than the lightning we see, but that could mean anywhere from 1/100th to 1/1000th as often, Smith said.

“It’s a very rough number,” Smith said. “The other question is, are there somewhat weaker ones that happen more often?”

Until those questions are answered, researchers say there’s no need for pilots to change course, since avoiding thunderstorms is already part of the gig. Depending on future findings, though, frequent flyers may want to watch the weather when they fly.

“It’s kind of cool that it’s been 250 years since Benjamin Franklin’s kite experiment, and we’ve realized there’s a different kind of lightning going on that we never knew about,” Dwyer said.